Angie Stone!!! Soulful, funky, sultry voice, halfway interesting lyrics even. But heavy on the soulful funk without sounding cheesy. I have her album "mahogany soul". Best of the "Neo Soul" genre, if you want to call it that. Even has decent recording quality and some real instruments.
Aside from that, Jill Scott - "who is Jill Scott?" is pretty good. Also check out Lina - "stranger on earth", who sounds the most like an original Billie Holiday without being an obvious copycat. India Arie isn't too bad, but she is pretty corny sometimes. Erykah Badu is popular, and surprisingly not as awful as her popularity might suggest.
For some reason, I never listen to male neo soul artists.